This invention relates to methods and arrangements for generating continuously changing random signals.
In many cases it is important to be able to generate a non-repetitive random reference signal for controlling certain events such as the speed of rotation of a machine of the type used for lapping the surfaces of balls for ball bearings or for altering the harmonic spectrum signature of a motor or a group of motors. In conventional systems a variable reference signal is generated in which the variation can be adjusted or selected manually from a rotary control or key pad.
The Fein U.S. Pat. No. 3,810,039 discloses a random signal generator containing first and second oscillators operating at two different frequencies in which the first oscillator output is sampled at the frequency of the second oscillator so that the output signal changes frequency from the first frequency to the second frequency periodically.
The Treadwell U.S. Pat. No. 3,384,834 discloses a frequency synthesizer containing two oscillators having different cyclic frequencies with the second oscillator output having upper and lower excursion limits which are determined by the first oscillator output. In the Dias U.S. Pat. No. 4,855,690 a random number generator has a first oscillator which varies the frequency of the output of a second, higher frequency oscillator. The Patent to Neri U.S. Pat. No. 4,107,683 discloses a motor controller circuit for controlling revolution of an antenna illuminator utilizing a reference signal generator and a digital random generator.
These prior art arrangements and methods are complex and expensive and do not provide the advantages of the present invention.
Accordingly it is an object of the present invention to provide a method and arrangement for generating continuously changing random signals which overcomes disadvantages of the prior art.
Another object of the invention is to provide a method and arrangement for generating continuously changing random signals in a simple and convenient manner.
These and other objects of the invention are attained by providing a random signal generating arrangement having two series-connected signal generators, the first signal generator producing a first signal having a signal level which changes in cycles between a maximum and minimum values at a first rate and the second signal generator producing a second signal which changes in cycles between maximum and minimum values at a substantially greater rate, in which the maximum level of the second signal in any cycle is determined by the instantaneous level of the first signal. Preferably, the minimum level of the second signal during any cycle is related to a selected fraction of the instantaneous level of the first signal. In a typical embodiment, the first and second signal generators have substantially the same circuit arrangement except for the size of capacitors that control the rate of change of the signal level of the output signal. Since the first signal is provided as an input to the second signal generator, the maximum and minimum values of the second signal follow a pattern which is determined by the continuously changing value of the first signal.